Conventional pneumatic cylinders provide a conduit for airflow into and out of the head and rod end volumes by means of ports machined into the respective head and rod end caps. Said ports serve as anchor points for plumbing that then communicates airflow to a control valve network. While such an arrangement has a certain level of operability, it typically creates a poor dynamic relationship between desired airflow and differential pressure. Consequently, attempts to apply such devices in precision applications have met with limited success.
Servo actuators with a continuously variable position output including a means to measure the position output. In the instance of a pneumatic servo cylinder, a sensor may be employed to measure the relative position between the moving element, for example a rod/piston assembly, and the frame to which a cylinder body is mounted. Conventionally, a hollow cylinder rod is employed so that position sensors, may be disposed within the cylinder, and partially nested within the cylinder rod. While this arrangement results in a pneumatic servo cylinder which is clean in appearance, and compact in size, hollow cylinder rods are more costly, and less structurally sound than their solid counterparts. Therefore, any position sensing means which may be integrated with the cylinder, while allowing for a solid cylinder rod, will have clear benefits.
To improve the dynamic relationship between desired airflow and differential pressure across the cylinder piston, the flow path from the control valve to the cylinder piston should be made as short and geometrically uniform as possible. Also, there is a need to improve manufacturing efficiencies in the production of the pneumatic servo cylinder while providing fewer flow path restrictions.